This invention relates to automatic optical alignment apparatus, and more particularly to such apparatus which senses the alignment condition of a remote body of interest and monitors the angular position thereof in three axes.
Automatic optical alignment instruments such as autocollimators are utilized for detecting very small changes in angular rotation of a reflective element such as a mirror, a retroreflective prism, or similar element which is mounted on a remote body whose alignment condition is of interest. The autocollimator is an optical instrument having a light source and a means for collimating a beam which is aimed at the reflector either directly or through a folded path and is reflected by the reflecting element with the reflected beam returning to the instrument nominally parallel to the emitted beam and then refocused to an image. Angular rotation of the remote element produces a movement of the image of the returning collimated beam which is applied to a detector and transformed into usable electrical signals providing an indication of the degree of rotation of the reflecting element. These signals can be utilized via suitable servomechanisms to align the rotating element or the signals may be used for some other purpose. The autocollimator described normally provides two-axis information and additional optical apparatus, for example, an automatic twist autocollimator which measures body rotation about the line of sight would be required to be incorporated with the automatic collimator already described in order to provide three axis information with respect to the angular movement of the reflector element. The combination of these instruments tends to be not only complex and costly but involves utilizing a common axis for making the measurements of the combined instruments whereby the multiple images following the same optical path may become contaminated and difficult to distinguish in order to provide the three axis information desired.